1. Field of the Invention
The present invention relates to a gasoline composition exhibiting an excellent detergent effects on the fuel intake system.
2. Description of the Background Art
Deposits and sludges produced in the fuel system and the combustion chamber of internal combustion engines are known to decrease the functions of the engines and also to have an adverse effect on exhaust gas. Deposits produced in intake valves and intake ports reduce output power of the engine, decrease driving performances, and increase the amount of exhaust gases. Performances of engines are being more and more promoted in recent years, and these high performance engines are more sensitive to these deposits.
Deposits in intake valves, in particular, cause serious problems in electronic controlled fuel injection systems, of which the use is recently increasing in passenger cars. Although these systems, which strictly control the fuel-air mixture, not only promote the engine performances but also are effective for energy saving and exhaust gas control, this fuel-air mixture control system ceases to correctly function if gasoline injected from the injection system comes into contact with deposits attached to the intake valves. The resulting malfunction of the fuel-air mixture control system seriously affects the drivability of the automobile.
Various gasoline additives are added to gasoline in order to prevent accumulation of deposits in fuel intake systems, such as carburetors and intake valves, to remove deposits therefrom, and to clean combustion chambers.
Compositions comprising a detergent, which is an oil-soluble active component containing a basic nitrogen such as amino group or amide group, and a carrier oil, which is typically a mineral or synthetic oil, are conventionally known as gasoline additive compositions. The detergent acts on soils and dirts which may deposit on the intake system to keep this system clean. The carrier oil is used to keep the detergent active. High boiling-point and high viscosity oils having excellent heat stability are usually used as a carrier oil. These oils have a function of a dispersing agent, by which the detergent is kept active. They also have a function of protecting metal surfaces in the intake system by forming liquid films. Polyolefins, polyoxyalkylenes (Japanese Patent Publication (kokoku) No. 48556/1981), esters, and the like are known as synthetic oils used as the carrier oil.
In order to adapt to engines of which the performances are more and more promoted in recent years, a high level of detergency is required for intake systems, particularly for intake valves. In particular, in order to enable the detergent to exhibit its actions more effectively, the carrier oil must be sufficiently heat resistant (intake valves are at 200.degree.-300.degree. C.), must have good compatibility with the detergent, and must well dissolve soils and dirts (oxidated or deteriorated matters from fuels and engine oils) in the intake system.
With the object of satisfying these requirements, some fuels and gasoline additives have been proposed, including (1) a fuel for internal combustion engines, in which two different types of compounds are used as carrier oils (Japanese Patent Application Laid-open (kokai) 173194/1990); (2) a fuel additive composition comprising a polyether amine-type compound (U.S. Pat. No. 5,018,029); and (3) a fuel additive composition comprising a polyether compound and a compound having an amine-type nitrogen atom and an oxyalkylene group or a polyamine (Japanese Patent Application Laid-open (kokai) 114089/1992).
These gasoline additives and gasoline compositions are not satisfactory in their detergent effects.
Development of a gasoline composition having a further improved detergent effect has therefore been desired.